1. Field of the Invention
The present invention relates generally to drilling methods, and, in particular, to telescopic drilling methods for use in connection with overburden drilling operations.
2. Description of Related Art
In order to collect and transfer water, wells are used and created by drilling a well hole or bore into the ground to an aquifer or water layer. As these bores are being drilled, often an overburden layer or rock layer is encountered and must be breached prior to reaching the water layer. In addition, the water layer often is far underground and requires special machinery and drilling equipment to reach.
Prior art drilling systems use long conduits, referred to as casings, welded together and gradually moved down the bore as it is drilled. However, the drilling operation creates stress on the casings and weld joints and may cause these casings to fracture. Such drilling impact and vibration stress is sustained by the rigid one-piece drill casing and its weld joints, causing cracks and fractures, which typically require the hole or bore to be cleared and the drilling process recommenced only after time and material expenditures.
Further, the present drilling methods are slow, as the drill is required to pull the entire casing length along with it as it penetrates further into the earth. This process is further slowed since the casing being pulled by the drill may be experiencing friction, pressure and contortions as a result of the outer walls of the bore collapsing and overburdened filling in against the casing. These deficiencies, exhibited by the prior art drills and the prior art drilling methods, decrease the drilling process efficiency and increases the xe2x80x9cwear and tearxe2x80x9d on the drilling machinery.
As the bores are often deep, the prior art drilling methods also require large and extended lengths of casings to be attached together, which causes the casing segments to stand high over the work area, and the drill rod segment must be loaded within the next casing section before it is transported and erected above the bore for welding to the preceding section. Such transport of the next casing segment containing the next drill rod segment is often precarious and results in human injury.
Present drilling methods require that the drilling by product and debris be expelled and managed high above ground level, with the use of a converter system which caps the top of the next casing section as it moves toward ground level during each drilling segment. Typically, a long overhead hose carries the debris from this converter system. However, this converter system must be removed and replaced for each drilling segment. Further, this converter system also stands high over the work site and poses an overhead hazard. In addition, there remains the possibility that the hose may entangle a person or machinery, and this overall converter system is complex and causes unnecessary delays in the drilling process.
Accordingly, it is an object of the present invention to provide a telescopic drilling method that overcomes these and other deficiencies in prior art drilling methods.
The present invention is a telescopic drilling method, and includes the steps of: (a) drilling an outer bore through a surface, the outer bore defined by an outer bore wall and an outer bore base and having an outer bore diameter and a first outer bore depth; (b) inserting a hollow outer conduit into the outer bore, the outer conduit having a drill end with a ring drill bit rotatably attached thereto; (c) at least partially inserting a first hollow inner conduit through the outer conduit; (d) preventing the first inner conduit from moving longitudinally with respect to the outer conduit; (e) engaging a rotatable inner drill bit with the ring drill bit, thereby creating a unitary drill bit head; (f) further drilling the outer bore using the unitary drill bit head to a successive outer bore depth; and (g) disengaging the inner drill bit from the ring drill bit, such that the outer conduit is capable of moving freely within the outer bore.
In the preferred embodiment, a second end of a successive hollow inner conduit is attached to a first end of an immediately preceding inner conduit, thereby creating an extended inner conduit, which is able to reach greater depths under the surface. The telescopic drilling method of the present invention is particularly useful in connection with overburden or rock drilling.